Improvement of Preparation Scheme for Microelectrode and Single Particle Electrochemical Measurements of LiCoO2 Interfaces Under Absence / Presence Chemical Additives

Abstract

Introduction Li-ion batteries (LIBs) are expected to stabilize the electrical power supply and utilize the electrical vehicle. Electrode of LIBs is consisted of mixture of active material, conductive additive, and binder. The conventional electrochemical measurement method is influenced not only by active materials but also by conductive additive and binder. Therefore, electrochemical measurement method with improved microelectrode in contact with single particle of active material was proposed［ 1 ］. This measurement method is generally known as single particle electrochemical measurement, and expected to evaluate the essential characteristics of active materials［ 2 ］. In this case, shapes and smooth of microelectrode are important factor in order to obtain the high-reliability results.In this study, we investigated the effects of microelectrode morphology and suitable contact with the surface of active materials. Experiments A Pt wire (φ30 µm) was inserted to glass capillary and was heated and cut to obtain supported fine line coating. Coated tip was polished by grinding machine and obtained well-prepared microelectrode (Fig.2(b)).An open cell was constructed in the argon-filled glovebox (-90℃ dew point). Li foil (φ10 mm) was put on the center of the stainless steel cup as a negative electrode, and a glass separator 110 µL electrolyte (1M-LiClO4/kg-PC) were added as electrolyte layer. LiCoO2 particles (20-30 µm diameter) were put onto electrolyte. The tip of microelectrode was directly attached to certain LiCoO2 single particle and charge / discharge measurements were carried out. Results & Discussion Fig.1 shows the charge / discharge profiles of the cell prepared by conventional process. Charge voltage did not reach the upper limited of 4.4V, and sufficient discharge profile was not observed.Fig.2 also shows the charge / discharge profiles of the cell prepared by new process. Reversible charge-discharge operation of single LiCoO2 particle was observed with appropriate capacity. Sufficient preparation prosses of the microelectrode was important for concise measurement of single particle electrochemical measurements. In the presentation, we will report detailed preparation method of microelectrode, and in-situ directly adding effect of chemical additives into the measurement cells.